I use a planet bike Alias (the one that goes up to 15w) combined with a Cat Eye Blinkie as a back up / be seen light. I usually run it on 15W on the dark (unlit) parts of the MUP, down to 10 on roads and on the lit parts of the trail. I like that it's simple, has an open bottom and so casts light on the road right in front of you in addition to way ahead, and the battery can't be over-charged.